Method and formulations for the manufacture of coated articles and composites

ABSTRACT

An object with a coating comprising: a) covalent bonds formed by reaction of a thiol group and a carbon-carbon double bond, b) covalent bonds formed by reaction of a thiol group and epoxide group, c) covalent bonds formed by a reaction of a carbon-carbon double bond and an epoxide group, said coating comprising a first primer coating and a second coating, said coating comprising covalent bonds between said first and second coatings, said first primer coating comprising covalent cross links between compounds, in the first coating the fraction (r3=ta/tc) of unreacted thiol groups (ta) to thiol groups which have reacted to form a covalent bond (tc) does not exceed 0.11, wherein the half height peak width of tan delta does not exceed 30° C. Advantages of the dual cure composition is that excellent strength is obtained and that the second curing is slow compared to the first initial curing.

This application is a continuation of PCT Application No.PCT/EP2013/059462, filed May 7, 2013, which claims priority of SE1200269-7, filed May 7, 2012, the entire contents of each of which arehereby incorporated by reference.

BACKGROUND

The present invention relates to the field of coating technology, inparticular a primer coating for the use with polymeric coating systemsfor materials including but not limited to wood, metals, rubber,thermoplastics, paper and textiles, where the primer retains reactivityfor a period of time after a first curing process is completed.

State of the art processes for fabricating multilayer coatings useactinic radiation in combination with photocurable prepolymercompositions that contain reactive monomers and oligomers, fillers andadditives such as leveling agents to rapidly achieve highly cross linkedpolymer coatings. Typically, multilayer coatings are composed of thinlayers that are applied in the wet state and cured sequentially. Toensure good adhesion between the wood or metal and the multilayercoating, a primer is usually employed. In the case of wood, this primeris sometimes waterborne to ensure good adhesion to the wood, and formetal, the primer layer is often a silane compound, where one end of themolecule covalently bonds to the metal substrate and the other end ofthe molecule covalently links with the first coatings layer.

To ensure adhesion between layers, state of the art processes utilize acontrolled level of oxygen inhibition to ensure that reactive compoundsremain to covalently bond to the next applied layer upon additionalcure.

In the art, off stoichiometry has long been well known and one patentdescribing thiol-ene polymers (U.S. Pat. No. 3,697,396) claimssignificantly off-stoichiometric mixtures, 0.5/1 to 2/1 ene to thiolratio, and gives examples of materials fabricated via significant offstoichiometry and reports curing time and shore hardness of saidmaterials. Single shaped molded cast articles from thiol-enes areclaimed, while micropatterning and assembly of articles from separatelyfabricated thiol-ene pieces are not mentioned.

Off stoichiometric formulations have been previously described in theart. In a work by Khire et al. (Adv. Mater. 2008, 20, 3308-3313), verythin nanopatterned off stochiometry thiol-ene films were fabricatedusing a nanopatterned PDMS stamp. The prepolymer contained a smallexcess of thiols and the thiol groups present on the polymer surfaceafter the polymerization was utilized for subsequent surfacemodification via a grafting-to process. Off stoichiometry was also usedto control the thickness of the grafted layer where, by adjusting thethiol to ene ratio, oligomers of a predetermined average size wherepolymerized in bulk and attached to the thiol excess polymer surface.While off stoichiometric formulations have been known in the art andsometimes are used, no systematic investigation into the properties ofoff-stoichiometric formulations have been performed. On the contrary, itis often argued that off-stoichiometry results in very poor mechanicalproperties, and should be avoided, (Belfield et al. ACS symposium series2003, p 65). The reasons for this are twofold: firstly deviation fromstoichiometry results in a non-optimized polymeric network with lessthan the maximum number of crosslinks and the inclusion of danglingchain ends; and secondly, there is a finite risk that monomers are leftunreacted in the network, thus risking leaching into the environment.

Ternary prepolymer formulations have been previously described in theart. Carioscia et al. (J. A. Carioscia et al., Polymer 48, (2007)1526-1532) described the cure kinetics and Tg of a ternary prepolymerformulation consisting of a thiol an allyl and an epoxide monomer. Inthe mixture there was also added a radical initiator and anionicinitiator. While good ultimate mechanical properties were achieved, noattempt to temporally separate the dual cure events to utilize theinherent reactivity after an initial cure was attempted nor was such astrategy suggested.

U.S. Pat. No. 5,821,305 discloses a cross linked epoxy resin, where theepoxy has been cross linked with a carboxylic anhydride, where theanhydride is a copolymer of an ethylenically unsaturated anhydride and avinyl compound. Triallylcyanurate is present.

U.S. Pat. No. 4,755,571 discloses a curable composition comprising anacrylic ester, an epoxide resin and a curing agent which can be apolymercaptan. The compositions can be used as adhesives and for fixingsurfaces together.

For micropatterning of polymers, commercial as well as in-housethiol-ene formulations using both molding and direct photolithographyhave been described in the art. In (D. Bartolo, et al, Lab Chip, 2008,8, 274) a method utilizing NOA 81, a commercially available thiol-enebased UV-curable glue, was shown to result in microfluidic devices, withadequate mechanical and bulk materials properties. Also good bonding toa substrate was shown upon renewed polymerization of an oxygen inhibiteduncured polymer layer situated on the bottom of the device. Furthermore,it was claimed that oxygen inhibition, due to the high gas permeabilityof the PDMS mold, was effective for creating a layer of unreactedprepolymer on the channel surfaces, which is useful for subsequentsurface modifications. In another example (J. Ashley et al. Lab Chip,2011, 11, 2772-2778), a freeform UV-curable photolithographic technologyusing thiol-enes was shown. Uniquely, the propensity for unwanted curein shadow regions exhibitied by thiol-enes, due to the high mobility ofradicals and low propensity for inhibition, was hindered by a largeamount of inhibitor added to the mixture.

WO 2012/042059 discloses a method of manufacturing articles comprisingreacting a compound comprising at least two thiol groups and a compoundcomprising at least two carbon-carbon double bonds in off stochiometryratios to obtain an intermediate article. That intermediate articlecomprises at least one unreacted group selected from an unreacted thiolgroup and an unreacted carbon-carbon double bond, and is subsequentlycontacted with a second article, wherein the surface of the secondarticle comprises reactive groups. Subsequently the unreacted groups onthe intermediate article are reacted with chemical groups on the secondarticle to obtain covalent bonds and forming a final article. The firstand/or the second article may also comprise at least one epoxide group.

SUMMARY

It is an object of the present invention to obviate at least some of thedisadvantages in the prior art and provide an improved coating as wellas an improved method.

In a first aspect there is provided a method for at least partiallycoating an object, said method comprising the steps: a) applying atleast partially to said object at least one of the following: A i. acompound comprising at least two thiol groups, ii a compound comprisingat least two carbon-carbon double bonds, and iii a compound comprisingat least two epoxide groups, and B I a compound comprising at least twothiol groups, ii a compound comprising at least one carbon-carbon doublebond and at least one epoxide group, wherein ratio (r1=t/cc) of thetotal number of thiol groups (t) in all of the above compounds and thetotal number of carbon-carbon double bonds (cc) in all of the abovecompounds is selected from the group consisting of 0.1≦r1≦0.9 and1.1≦r1≦20, with the proviso that if the ratio r1 is in the interval:0.1≦r1≦0.9, then at least one homopolymerizing ene-compound is used,wherein ratio (r2=t/e) of the total number of thiol groups (t) in all ofthe above compounds and the total number of epoxide groups (e) in all ofthe above compounds is in the range 0.3≦r2≦20, b) initiating a reactionof at least a part of the applied compound comprising at least two thiolgroups with at least one of i at least a part of the applied compoundcomprising at least two carbon-carbon double bonds and, ii at least apart of the applied compound comprising at least two epoxide groups, iiiat least a part of the applied compound comprising at least onecarbon-carbon double bond and at least one epoxide group, to obtain anintermediate at least partial coating, wherein said coating comprises atleast one compound comprising an unreacted group selected from the groupconsisting of an unreacted thiol group, and an unreacted epoxide group,c initiating a reaction of at least a part of said at least one compoundcomprising an unreacted group, wherein at least one further coating isapplied at at least one point selected from the group consisting ofafter step b) and after step c), to obtain to a final coated article.

In a second aspect there is provided a coated object comprising acoating which are at least partially applied to said object, saidcoating comprising: a) covalent bonds formed by reaction of a thiolgroup and a carbon-carbon double bond, b) covalent bonds formed byreaction of a thiol group and epoxide group, c) covalent bonds formed bya reaction of a carbon-carbon double bond and an epoxide group, saidcoating comprising a first coating and a second coating, said coatingcomprising covalent bonds between said first and second coatings, saidfirst coating comprising covalent cross links between compounds, in thefirst coating the fraction (r3=ta/tc) of unreacted thiol groups (ta) tothiol groups which have reacted to form a covalent bond (tc) does notexceed 0.11, wherein, for the first coating the half height peak widthof tan delta does not exceed 30° C., said tan delta peak temperature(Tp) (Tp=Tg) and said half height peak width being obtained from aviscoelasticity (tan delta) temperature distribution curve which isdetermined using a viscoelastic spectrometer at a frequency of 1 Hz, aninitial strain of 0.1%, an amplitude of 15 μm and a temperatureelevating rate of 5° C./min, temperatures being equal to and greaterthan Tp to the temperature defined by the point of intersection of theline of tan delta=1/2P, wherein P is the peak value of tan δ, with thedistribution curve.

Further aspects and embodiments are defined in the appended claims,which are specifically incorporated herein by reference.

One advantage is that the first applied coating (primer) retainsreactivity for a period of time after a first curing process iscompleted.

Another advantage is that excellent adhesion strength is achieved due tocovalent bonding.

Yet another advantage is that excellent mechanical properties ascompared with off stoichiometry or stoichiometry thiol-enes with higherultimate Tg and higher Young's modulus are obtainable due to a largenumber of hydrogen bonds and very high crosslink densities.

The primer coatings have very low residual stress compared with state ofthe art coatings, which results in more durable coatings.

Another advantage is that there are very little leachable monomers(compared with off stoichometry thiol-enes, acrylates and methacrylates)due to very high conversion of functional groups.

It is possible to obtain excellent barrier properties due to very highcrosslink densities.

Due to the dual curing there is reduced stress in subsequent coatingsdue to a rubbery modulus after the first cure (allows for the subsequentcoating to “glide” on top of the primer coating after the first cure).

Narrow Tan delta peaks extends the usage temperature range to very closeto Tg.

Tunable ultimate Tg and Young's modulus allows for optimized primerformulations with respect to the substrate's Young's modulus.

High strain until break, as compared with standard acrylateformulations, allows for primers that withstand small deformationswithout cracking.

The possibility to obtain excellent optical clarity allows for primerson transparent or white substrates without or with minimaldiscoloration.

Less oxygen inhibition compared to acrylates and methacrylates allowsfor very thin primer layers without detrimental effects due to partialinhibition of polymerization by oxygen.

Less moisture sensitivity compared with cationically curing systemsallows for even coatings quality under varying ambient conditions.

Highly compatible with many types of filler particles due to covalentlinkages between the polymer matrix and the particles due to thecomplementary reactivity of thiols and anionically cured epoxies.

DETAILED DESCRIPTION

Before the invention is disclosed and described in detail, it is to beunderstood that this invention is not limited to particular compounds,configurations, method steps, substrates, and materials disclosed hereinas such compounds, configurations, method steps, substrates, andmaterials may vary somewhat. It is also to be understood that theterminology employed herein is used for the purpose of describingparticular embodiments only and is not intended to be limiting since thescope of the present invention is limited only by the appended claimsand equivalents thereof.

It must be noted that, as used in this specification and the appendedclaims, the singular forms “a”, “an” and “the” include plural referentsunless the context clearly dictates otherwise.

If nothing else is defined, any terms and scientific terminology usedherein are intended to have the meanings commonly understood by those ofskill in the art to which this invention pertains.

The term “about” as used in connection with a numerical value throughoutthe description and the claims denotes an interval of accuracy, familiarand acceptable to a person skilled in the art. Said interval is ±10%.

In a first aspect there is provided a method for at least partiallycoating an object, said method comprising the steps:

-   -   a) applying at least partially to said object at least one of        the following:        -   A            -   i. a compound comprising at least two thiol groups,            -   ii. a compound comprising at least two carbon-carbon                double bonds, and            -   iii. a compound comprising at least two epoxide groups,                and        -   B            -   i. a compound comprising at least two thiol groups,            -   ii. a compound comprising at least one carbon-carbon                double bond and at least one epoxide group,        -   wherein ratio (r₁=t/cc) of the total number of thiol            groups (t) in all of the above compounds and the total            number of carbon-carbon double bonds (cc) in all of the            above compounds is selected from the group consisting of            0.1≦r₁≦0.9 and 1.1≦r₁≦20,        -   with the proviso that if the ratio r₁ is in the interval:            0.1≦r₁≦0.9, then at least one homopolymerizing ene-compound            is used,        -   wherein ratio (r₂=t/e) of the total number of thiol            groups (t) in all of the above compounds and the total            number of epoxide groups (e) in all of the above compounds            is in the range 0.3≦r₂≦20,    -   b) initiating a reaction of at least a part of the applied        compound comprising at least two thiol groups with at least one        of        -   i. at least a part of the applied compound comprising at            least two carbon-carbon double bonds and,        -   ii. at least a part of the applied compound comprising at            least two epoxide groups,        -   iii. at least a part of the applied compound comprising at            least one carbon-carbon double bond and at least one epoxide            group,    -   to obtain an intermediate at least partial coating, wherein said        coating comprises at least one compound comprising an unreacted        group selected from the group consisting of an unreacted thiol        group, and an unreacted epoxide group,    -   c) initiating a reaction of at least a part of said at least one        compound comprising an unreacted group,        -   wherein at least one further coating is applied at at least            one point selected from the group consisting of after            step b) and after step c), to obtain to a final coated            article.

In one embodiment the reaction between at least a part of the appliedcompound comprising at least two thiol groups and at least a part of theapplied compound comprising at least one or two carbon-carbon doublebonds is initiated with at least one selected from the group consistingof actinic radiation, and elevated temperature. In one embodiment thereaction of the at least one compound comprising an unreacted groupselected from the group consisting of an unreacted thiol group and anunreacted epoxide group is initiated with at least one selected from thegroup consisting of actinic radiation, and elevated temperature. In oneembodiment the reaction of the at least one compound comprising anunreacted group selected from the group consisting of an unreacted thiolgroup and an unreacted epoxide group is mediated with a basic compound.

In one embodiment step b) and c) are initiated simultaneously.Alternatively step b is initiated first and step c is initiatedafterwards. In yet another embodiment step c is initiated first andsubsequently step b is initiated. The reaction initiated in step b isrelatively quick and the reaction initiated in step c is relativelyslow. In this respect quick and slow relates to the other reaction, i.e.the reaction in step b is quicker than the reaction in step c. The timefor the reaction is measured until no further reactions occur. When boththe reaction in step b) and the reaction in step c) have completed, morethan 90% of the thiol groups have reacted to form covalent bonds. Oftenmore than 95% of the thiol groups or even more than 99% of the thiolgroups form covalent bonds.

In one embodiment the at least one further coating comprises at leastone compound selected from the group consisting of a compound reactivewith a thiol forming a covalent bond and a compound reactive with anepoxide to form a covalent bond. In one embodiment the at least onefurther coating comprises at least one compound comprising at least onechemical group selected from the group consisting of a hydroxyl group,an amine group, a thiol group, an anhydride group, a cyanoacrylategroup, an epoxide group, and a metal oxide. In one embodiment the atleast one further coating comprises at least one compound comprising achemical group selected from the group consisting of an acrylate, amethacrylate, a thiol, an isocyanate, a maleate, a fumarate, a vinylether, an alkene, an alkyne, an allyl ether. In one embodiment the atleast one further coating comprises at least one selected from the groupconsisting of a metal, a polymer sheet, and a powder.

In one embodiment the surface of said object to be at least partiallycoated comprises at least one selected from the group consisting of ametal, a rubber, silicon, a thermoplastic elastomer, cellulose fibers, atextile, wood, a composite material, concrete, and stone.

In one embodiment the object to be at least partially coated is aprinted circuit board.

In one embodiment the compound comprising at least two thiol groups isselected from the group consisting of pentaerythritol tetrakis(2-mercaptoacetate), pentaerythritol tetramercaptopropionate (PETMP);1-octanethiol; butyl 3-mercaptopropionate;2,4,6-trioxo-1,3,5-triazina-triy (triethyl-tris (3-mercapto propionate);1,6-Hexanedithiol; 2,5-dimercaptomethyl-1,4-dithiane, pentaerythritoltetramercaptoacetate, trimethylolpropane trimercaptoacetate,2,3-dimercapto-1-propanol, 2,3-(dimercaptoethylthio)-1-mercaptopropane,1,2,3-trimercaptopropane, toluenedithiol, xylylenedithiol,1,8-octanedithiol, and trimethylolpropane tris(3-mercaptopropionate),and glycol dimercaptopropionate and pentaerythritoltetramercaptopropionate (PETMP)

In one embodiment the compound comprising at least two carbon-carbondouble bonds is selected from the group consisting oftriallyl-1,3,5-triazine-2,4,6(1H,3H,5H)-trione; triethyleneglycoldivinyl ether (TEGDVE); trimethylolpropane diallyl ether;1,6-heptadiyne; 1,7-octadiyne;bis-2,2-[4-(2-[norborn-2-ene-5-carboxylate]ethoxy)phenyl]propane(BPAEDN); 1,6-hexanediol di-(endo,exo-norborn-2-ene-5-carboxylate)(HDDN); trimethylolpropane tri-(norborn-2-ene-5-carboxylate) (TMPTN);pentaerythritoltri-(norborn-2-ene-5-carboxylate) (PTN3); pentaerythritoltetra-(norborn-2-ene-5-carboxylate) (PTN4); tricyclodecane dimethanoldi-(endo, exo-norborn-2-ene-5-carboxylate) (TCDMDN); anddi(trimethylolpropane) tetra-(norbom-2-ene-5-carboxylate) (DTMPTN).

In one embodiment the compound comprising at least two epoxide groups isselected from the group consisting of Tris(2,3-epoxidepropyl)isocyanurate, trimethylolpropane triglycidyl ether,tris(4-hydroxyphenyl)methane triglycidyl ether, poly(ethylene glycol)diglycidyl ether, bisphenol A diglycidyl ether1,2,5,6-diepoxidecyclooctane, 1,2,7,8-diepoxideoctane,1,2-Epoxide-5-hexene, 1,4-cyclohexanedimethanol diglycidyl ether,3,4-epoxidecyclohexylmethyl 3,4-epoxidecyclohexanecarboxylate,4,4′-methylenebis(N,N-diglycidylaniline),bis[4-(glycidyloxy)phenyl]methane, bis[4-(glycidyloxy)phenyl]methane,diglycidyl 1,2-cyclohexanedicarboxylate,N,N-diglycidyl-4-glycidyloxyaniline, neopentyl glycol diglycidyl ether,resorcinol diglycidyl ether, and tris(4-hydroxyphenyl)methanetriglycidyl ether.

In one embodiment the compound comprising at least two epoxide groups isallylglycidylether.

In one embodiment compounds mentioned under A are used, i.e. i) acompound comprising at least two thiol groups, ii) a compound comprisingat least two carbon-carbon double bonds, and iii) a compound comprisingat least two epoxide groups. In an alternative embodiment compoundsmentioned under B are used, i.e. i) a compound comprising at least twothiol groups, and ii) a compound comprising at least one carbon-carbondouble bond and at least one epoxide group. In yet another embodimentcompounds mentioned under both A and B are used.

In one embodiment the thickness of the compounds added in step a is inthe interval 2-100 μm. If the compounds are added partially thethickness is measured only for the parts where compounds are added.Areas of the object which are not coated are not used for thecalculation of the thickness. The thickness is calculated as an averagethickness for the areas where the compounds are applied.

In a second aspect there is provided a coated object comprising acoating which are at least partially applied to said object, saidcoating comprising: a) covalent bonds formed by reaction of a thiolgroup and a carbon-carbon double bond, b) covalent bonds formed byreaction of a thiol group and epoxide group, c) covalent bonds formed bya reaction of a carbon-carbon double bond and an epoxide group,

said coating comprising a first coating and a second coating,said coating comprising covalent bonds between said first and secondcoatings,said first coating comprising covalent cross links between compounds,in the first coating the fraction (r₃=ta/tc) of unreacted thiol groups(ta) to thiol groups which have reacted to form a covalent bond (tc)does not exceed 0.11,wherein for the first coating the half height peak width of tan deltadoes not exceed 30° C., said tan delta peak temperature (Tp) and saidhalf height peak width being obtained from a viscoelasticity (tan delta)temperature distribution curve which is determined using a viscoelasticspectrometer at a frequency of 1 Hz, an initial strain of 0.1%, anamplitude of 15 μm and a temperature elevating rate of 5 degC/min,temperatures being equal to and greater than Tp to the temperaturedefined by the point of intersection of the line of tan delta=1/2P,wherein P is the peak value of tan δ, with the distribution curve.

There is a standard for determination of the half height peak width oftan delta: ASTM 1640. The above described method deviates slightlyregarding the temperature change.

In one embodiment of the second aspect the second coating comprises atleast one compound comprising at least one chemical group selected fromthe group consisting of a hydroxyl group, an amine group, a thiol group,an anhydride group, a cyanoacrylate group, an epoxide group, and a metaloxide. In one embodiment of the second aspect the second coatingcomprises at least one compound comprising a chemical group selectedfrom the group consisting of an acrylate, a methacrylate, a thiol, anisocyanate, a maleate, a fumarate, a vinyl ether, an alkene, an alkyne,an allyl ether. In one embodiment of the second aspect the secondcoating comprises at least one selected from the group consisting of ametal, a polymer sheet, and a powder.

In one embodiment of the second aspect the surface of the objectcomprises at least one selected from the group consisting of a metal, arubber, silicon, a thermoplastic elastomer, cellulose fibers, a textile,wood, a composite material, concrete, and stone.

In one embodiment of the second aspect the at least partially coatedobject is a printed circuit board.

In one embodiment of the second aspect the first coating comprises atleast one compound selected from the group consisting of pentaerythritoltetrakis (2-mercaptoacetate), pentaerythritol tetramercaptopropionate(PETMP); 1-octanethiol; butyl 3-mercaptopropionate;2,4,6-trioxo-1,3,5-triazina-triy (triethyl-tris (3-mercapto propionate);1,6-Hexanedithiol; 2,5-dimercaptomethyl-1,4-dithiane, pentaerythritoltetramercaptoacetate, trimethylolpropane trimercaptoacetate,2,3-dimercapto-1-propanol, 2,3-(dimercaptoethylthio)-1-mercaptopropane,1,2,3-trimercaptopropane, toluenedithiol, xylylenedithiol,1,8-octanedithiol, and trimethylolpropane tris(3-mercaptopropionate),and glycol dimercaptopropionate and pentaerythritoltetramercaptopropionate (PETMP), wherein at least one thiol group hasformed a covalent bond with at least one selected from a carbon-carbondouble bond and an epoxide group.

In one embodiment of the second aspect the first coating comprises atleast one compound selected from the group consisting oftriallyl-1,3,5-triazine-2,4,6(1H,3H,5H)-trione; triethyleneglycoldivinyl ether (TEGDVE); trimethylolpropane diallyl ether;1,6-heptadiyne; 1,7-octadiyne;bis-2,2-[4-(2-[norborn-2-ene-5-carboxylate]ethoxy)phenyl]propane(BPAEDN); 1,6-hexanediol di-(endo,exo-norborn-2-ene-5-carboxylate)(HDDN); trimethylolpropane tri-(norborn-2-ene-5-carboxylate) (TMPTN);pentaerythritoltri-(norborn-2-ene-5-carboxylate) (PTN3); pentaerythritoltetra-(norborn-2-ene-5-carboxylate) (PTN4); tricyclodecane dimethanoldi-(endo, exo-norborn-2-ene-5-carboxylate) (TCDMDN); anddi(trimethylolpropane) tetra-(norbom-2-ene-5-carboxylate) (DTMPTN),wherein at least one carbon-carbon double bond has formed a covalentbond with at least one selected from a thiol group and an epoxide group.

In one embodiment of the second aspect the first coating comprises atleast one compound selected from the group consisting ofTris(2,3-epoxidepropyl) isocyanurate, trimethylolpropane triglycidylether, tris(4-hydroxyphenyl)methane triglycidyl ether, poly(ethyleneglycol) diglycidyl ether, bisphenol A diglycidyl ether1,2,5,6-diepoxidecyclooctane, 1,2,7,8-diepoxideoctane,1,2-Epoxide-5-hexene, 1,4-cyclohexanedimethanol diglycidyl ether,3,4-epoxidecyclohexylmethyl 3,4-epoxidecyclohexanecarboxylate,4,4′-methylenebis(N,N-diglycidylaniline),bis[4-(glycidyloxy)phenyl]methane, bis[4-(glycidyloxy)phenyl]methane,diglycidyl 1,2-cyclohexanedicarboxylate,N,N-diglycidyl-4-glycidyloxyaniline, neopentyl glycol diglycidyl ether,resorcinol diglycidyl ether, and tris(4-hydroxyphenyl)methanetriglycidyl ether, wherein at least one epoxide group has formed acovalent bond with at least one selected from a thiol group and acarbon-carbon double bond.

In one embodiment of the second aspect the thickness of the coating isin the interval 0.01-2000 μm. The thickness of the coating is the totalthickness of the first coating (the primer) and the second coating. Thethickness of the first coating is in one embodiment in the interval0.005-500 μm. The thickness of the second coating is in one embodimentin the interval 0.005-1500 μm. The thickness of the coatings mentionedin this paragraph refer to the thickness after the curing reactions havecompleted.

The invention provides the means for formulating and using coatingssystems that comprise a primer (first coating) and a further coating(second coating) applied to various materials. The individual coatinglayers that form a final multilayer coating comprise, for at least oneof the coatings layers, chemical compounds that provide dual curecapability, i.e. a system where a first reaction provides intermediatemechanical and chemical properties and a second cure that provides finalmechanical and chemical properties. In this manner, a solid orsemi-solid coating with multitude reactive groups is present after afirst, rapid, curing step, and a hard, inert coating layer which iscovalently linked with the further coating is present after a secondcuring step, where the completion of the cure is delayed in timecompared with the completion of the first cure.

The components of the coating in step a are applied either in as apre-mixed mixture or as separate components. Alternatively thecomponents are applied both a as a mixture comprising all or some of thecompounds and as one or more separate components comprising theremaining ingredients.

The ratios r1, r2, and r3 are calculated as number ratios based on thecompounds that fall under the general definitions of compounds in step ain claim 1. I.e. for r1 the number of thiol groups t in all compoundswhich fall under the compounds mentioned in claim 1 are counted, alsothe number of number of carbon-carbon double bonds cc (ene groups) inall compounds which fall under the compounds mentioned in claim 1 arecounted. Then the ratio r1=t/cc is calculated. If for instance acompound containing only 1 thiol group is present it does not fall undercompounds in claim 1 and is thus not counted.

When the ratio r₁ is in the interval 0.1≦r₁≦0.9 at least onehomopolymerizing ene-compound is used in the coating. It is addedtogether with the other ingredients of the primer coating. In oneembodiment the at least one homopolymerizing ene-compound is selectedfrom the group consisting of acrylate and methacrylate. An ene-compoundcomprises a carbon-carbon double bond.

In step b and c the reactions are initiated. This means that they arestarted, and the reactions can take a certain time to finish. When theboth of the reactions initiated in step b and step c are finished morethan 90% of the number of thiol groups have reacted, preferably morethan 95%, more preferably more than 99%. Especially the reactioninitiated in step c, is slower so that covalent bonds can be formed withthe at least one further coating which is applied. In one embodiment thereaction in step c can be initiated and thereafter the coating can beapplied. Then the reaction has not finished, but only proceeded to alimited extent when the further coating is applied, so that covalentbond with the further coating can be formed. Alternatively the furthercoating can be applied after step b and the second curing reaction canbe initiated in step c after the further coating has been applied. Thecomposition has a dual cure formulation composed of thiol-ene-epoxide.

The applied compounds in step a) will form a coating which can be calleda primer, which binds the coating to the object to be coated and whichalso bind to the further coating which is applied on the primer.

In one embodiment, a wood surface is coated. An example of wood includesbut is not limited to wood boards intended to be used on floors.

In one embodiment industrial application methods is used to apply thecompounds in step a, including but not limited to methods such as spraycoating, curtain coating or rolling, in a thin layer in one embodimenttypically ranging between 2-100 microns (μm) thick. This refers to thecompounds applied in step a and before any curing reactions areinitiated. As mentioned the compounds can either be added in a mixtureor separately.

In one embodiment the thiol is in stoichiometric excess compared withthe ene and epoxide component respectively and stoichiometric overallwith respect to thiol to ene plus epoxide. Ene refers to a carbon-carbondouble bond. After application of the first layer, actinic radiation ormoderated heat is used to initiate a radically mediated thiol-enepolymerization, and a partially polymerized semi-solid or solid polymer,with many reactive thiol and epoxide groups dispersed throughout thepartially polymerized polymer, is formed. Depending on the processrequirements, the second reaction is initiated simultaneously with theradically mediated polymerization, or initiated in a subsequent separateinitialization event. In one embodiment the second reaction isanionically initiated with a pH above 7.

In one embodiment, after the first coating layer is applied and curedvia radically mediated thiol-ene polymerization, a second layer, thatmay be of similar or the same composition as the first layer, or anothercomposition reactive either with thiols, e.g. acrylate or methacrylatefunctional prepolymers, or epoxies, e.g. anhydride, thiol, isocyanate oramine functional prepolymers, is applied on top of the first coating. Inone embodiment, after the second coating, typically actinic radiation orheat is applied to initiate a radically mediated cure of the secondlayer, whereupon covalent links are formed to the pendant thiol groupsremaining in the first layer. In an alternative embodiment the secondcuring reaction is started at the same time as the first curing reactionor before the second layer is applied, however since the first curingreaction is faster than the second the first curing reaction will becompleted first. In one embodiment the second curing reaction will becompleted after the second layer is applied.

In a similar manner additional layers are in alternative embodimentsadded until the desired coating is produced.

Upon completion of the cure of the last layer, the second epoxide-thiolreaction, either initiated via heat or actinic radiation, is brought tocompletion to impart final mechanical and chemical properties and ensurecovalent bonding via epoxide reactions with the hydroxyl groups presenton wood components such as cellulose and thiol reactions to enecomponents present in wood resin components such as terpenes. As analternative the second epoxide-thiol reaction is initiated with additionof a strong base and being at room temperature.

In one embodiment, metals are coated, using the method described above.The adhesion to the substrate, i.e. the surface of the object to becoated is provided by epoxide reaction with primarily metal hydratespresent on most metal surfaces, or in an alternative embodiment viathiol links that covalently bond to gold, platinum etc.

In another embodiment, rubber substrates are coated, using the methoddescribed above. The adhesion to the substrate is provided by thiolreactions with double bonds present in for example natural rubber,polyisoprene etc.

In another embodiment, thermoplastic elastomers are coated, using themethod described above. The adhesion to the substrate is provided bythiol reactions with double bonds present in the rubbery segments of thethermoplastic elastomers.

In another embodiment, thermoplastic substrates are coated, using themethod described above. The adhesion to the substrate is typicallyprovided by epoxide reactions with the hydroxyl groups or active oxygengroups that result from plasma or corona treatment of thermoplasticsurfaces.

In another embodiment, cellulose fiber based materials, e.g. paper, arecoated and impregnated by the prepolymer formulations to form compositestructures upon cure using the method described above. The adhesion tothe fibers is typically provided by covalent bonding via epoxidereactions with the hydroxyl groups present on cellulose fibers.

In another typical embodiment, textile fiber based materials, e.g. wovenmaterials, cloth etc., are coated and impregnated by the prepolymerformulations to form composite structures upon cure using the methoddescribed above. The adhesion to the fibers is typically provided byepoxide reactions with the hydroxyl or amine and amide groups present inmany woven materials.

The embodiments described above can varied in terms of curing order, theuse of two component prepolymer systems with various compositions of thetwo components, pre-treatment of the wood or metal, e.g. sanding of thewood etc. and etching of the metal etc. and corona treatment ofplastics, room temperature conditions and other variations that areeasily implemented to experts in the respective fields.

Eligible functional groups used to fabricate coating layers are thosethat participate in essentially alternating copolymerizations. In oneembodiment monomers are multifunctional thiol monomers as the onecomponent, an -ene (e.g. vinyl ether, norbornene and allyl ether) as thesecond component and epoxide as a third component. By off-stoichiometryformulation of the first, second and third components, i.e. the thiolcomponent is in excess to the epoxide and ene respectively, surplusthiol and epoxide groups are present throughout the polymeric networkupon completion of a first radically mediated thiol-ene polymerizationprocess. Until completion of the second polymerization process, thioland epoxide groups react within the coating layer, with adjacent coatinglayers and chemical moieties on the surface of the substrate, e.g.hydroxyl groups naturally present in both wood and metals such asaluminum, stainless steel, copper, gold etc. Alternatively, thethiol-epoxide polymerization process is completed first resulting in apartially cured material with a multitude of thiol and ene functionalgroups that are converted into a crosslinked material, with only a fewene, thiol and epoxide groups left, via a subsequent radically mediatedreaction.

As an alternative the compound comprising at least two epoxide groupsand the compound comprising at least two carbon-carbon double bonds isreplaced by one compound comprising at least one epoxide group and atleast one carbon-carbon double bond. In yet another alternative both acompound comprising at least one epoxide group and at least onecarbon-carbon double bond and compounds comprising at least twocarbon-carbon double bond and compounds comprising at least two epoxidegroups are added together with the compound comprising at least twothiol groups.

In one embodiment, the invention provides wood and metal coatingscomposition with thiol-ene-epoxide liquid polymer precursors andsuitable initiators where a first radically mediated polymerizationprovides a partially crosslinked polymer network with a multitude ofthiol and epoxide groups present and a second anionically mediatedpolymerization provides a crosslinked network with very few remainingene, thiol and epoxide groups.

In another embodiment, the coated substrate is a rubber that containsgroups reactive to either of the functional groups present in theprepolymer formulation, e.g. thiol/ene/epoxide.

In yet another embodiment, the coated and/or impregnated substrate iscomposed largely of cellulose fibers.

In still another embodiment, the coated and/or impregnated substrate iscomposed largely of textile fibers.

In one embodiment the coatings composition comprises thiol-ene-epoxideliquid polymer precursors and suitable initiators, inhibitors, fillersand additives such as leveling agents, where a first radically mediatedpolymerization provides a partially crosslinked polymer network with amultitude of thiol and epoxide groups present and a second anionicallymediated polymerization provides a crosslinked network with very fewremaining ene, thiol and epoxide groups. In one embodiment a silane isused as additive.

In an alternative embodiment formulations are stoichiometric overallsuch that the number of thiol groups is essentially equal to the numberof ene-groups plus the epoxide groups, e.g. 1/0.5/0.5 or 1/0.7/0.3 or1/0.4/0.6 etc. with respect to the normalized to thiol number ofthiol/ene/epoxide groups.

In one embodiment formulations are non-stoichiometric overall, e.g.1/0.5/0.7 or 1/0.3/0.5 or 1/0.5/0.8 etc. with respect to the normalizedto thiol number of thiol/ene/epoxide groups.

In one embodiment the initiators are of an alpha cleaving type forradically mediated polymerization, and of a thermally or photo-latenttype base for the anionically mediated reaction.

In another embodiment the initiators are of an alpha cleaving type forradically mediated polymerization, and of a base type, e.g. DBN or otheramine compounds for the anionically mediated reaction.

In yet another embodiment the initiators are of a hydrogen abstractiontype for radically mediated polymerization, and of a base type, and of athermally or photo-latent type base for the anionically mediatedreaction.

In one embodiment, initiation of the anionically mediated reaction isperformed by providing a reactive surface, e.g a silanized aminesurface, or by applying a reactive solution or coating that containschemical species capable of initiating anionically mediatedpolymerization.

Combinations of the above initiator types and methods are also useful inthe invention.

In one embodiment, the coating comprises thiol-ene-epoxide liquidpolymer precursors and suitable initiators, inhibitors, fillers andadditives such as leveling agents, in a two component system, where afirst component comprises thiol-ene monomers, an anionic initiator and aradical initiator and the second component comprises thiol-ene-epoxidemonomers, where at least one of the polymerization reactions isinitiated upon mixing of the two components.

In another embodiment, the coating comprising thiol-ene-epoxide liquidpolymer precursors and suitable initiators, inhibitors, fillers andadditives such as leveling agents is diluted with a suitable solvent toimpart desired viscosity, e.g. for spray coating or curtain coating.Apart from the additional step of solvent removal, the use of thediluted formulation follows either of the previously describedembodiments.

In one embodiment the reaction in step b) and/or step c) in claim 1 isinitiated with an initiator. Examples of initiators that produceradicals include, but are not limited to, Rose Bengal (Aldrich), Darocur2959 (2-hydroxy-1-[4-(hydroxyethoxy)phenyl]-2-methyl-1-propanone, D2959,Ciba-Geigy), Irgacure 651 (2,2-dimethoxy-2-phenylacetophenone, 1651,DMPA, Ciba-Geigy), Irgacure 184 (1-hydroxycyclohexyl phenyl ketone,1184, Ciba-Geigy), Irgacure 907(2-methyl-1-[4-(methylthio)phenyl]-2-(4-morpholinyl)-1-propanone, 1907,Ciba-Geigy), Camphorquinone (CQ, Aldrich), isopropyl thioxanthone(quantacure ITX, Great Lakes Fine Chemicals LTD., Cheshire, England),Kip 100 and 150 from Fratelli-Lamberti, Darocur 11732-Hydroxy-2-methyl-1-phenyl-propan-1-one (Ciba Specialty Chemicals), andphosphine oxides such as IrgacureBis(2,4,6-trimethylbenzoyl)-phenylphosphineoxide 819 (Ciba). CQ istypically used in conjunction with an amine such as ethyl4-N,N-dimethylaminobenzoate (4EDMAB, Aldrich) or triethanolamine (TEA,Aldrich) to initiate polymerization, for the anionic step a photolatentDBN from BASF is preferred. Photolatent DBN is typically used inconjunction with benzophenone or ITX.

Initiators for a thermally initiated or thermally accelerated cureinclude but are not limited to DBN, DMP-30 and tertiary amines. In oneembodiment the elevated temperature treatment is about 70° C. during twohours. In one embodiment the radiation is used during 3-100 seconds.Radiation dose varies from 30 mJ/cm² to 1 J/cm².

The compounds used for the coating in one embodiment are i) adifunctional or multifunctional thiol monomers or mixtures of monomerswith an average functionality ≧2 and ii) a difunctional ormultifunctional -ene (e.g. vinyl ether, norbornene and allyl ether) ormixtures of -ene monomers with an average functionality ≧2, and iii) adifunctional or multifunctional epoxide monomers or mixtures of monomerswith an average functionality ≧2. By off-stoichiometry formulation, i.e.either one component in excess, surplus reactive groups are presentthroughout the polymeric network upon completion of the firstpolymerization process. The compounds used for coating can be referredto as monomers since they are involved in a polymerization process. Theformation of covalent bond between the compounds can be viewed as apolymerization process, since result will be a kind of cross linkednetwork.

Optionally there are applied further substances, examples include butare not limited to fillers, additives, solvents, pigments, polymers, andoligomers.

The barrier properties of the coating are excellent and thus the coatingcan be used to form a barrier intended to be impermeable to liquid.Potential uses are within food packages for liquids, and other types offood. Thus in one embodiment the coating can form a barrier impermeableto liquid.

Other features and uses of the invention and their associated advantageswill be evident to a person skilled in the art upon reading thedescription and the examples.

It is to be understood that this invention is not limited to theparticular embodiments shown here. The following examples are providedfor illustrative purposes and are not intended to limit the scope of theinvention since the scope of the present invention is limited only bythe appended claims and equivalents thereof.

EXAMPLES Example 1 Adhesion Tests

Adhesion tests (according to ISO 2409) were performed to evaluate theadhesion of the primer on different substrate materials. Three differentformulations of thiol-ene-epoxy were used based on1,3,5-Triallyl-1,3,5-triazine-2,4,6(1H,3H,5H)-trione (TATATO),KarentzMT™ PEI, Pentaerythritol tetrakis (3-mercaptobutylate) (PTMB)from ShowaDenko, Japan, Epoxy Novolac D.E.N. 431 (DEN) from Enorica GmbHwith epoxy equivalent weight: 172-179, epoxide percentage %: 24-25. Oneformulation thiol-methacrylate-epoxy, based on1,4-Butanedioldimethacrylate was also tested.

In formulation 1 and 2 the ratio between thiol and allyl was r1=1.8, andbetween epoxy and thiol r2=0.4. In formulation 3 the functional rationbetween thiol and allyl was r1=1.8 and between epoxy and thiol r2=0.67.In formulation 4 the ration between thiol and metacrylate was r1=0.4 andbetween epoxy and thiol r2=2.25. As initiators were added 2 w % Lucirin™TPO-L (BASF, Germany), 4 w % Benzophenone and 2 w % of a photo-latentversion of 1,5-diazabicyclo[4.3.0]-non-5-ene (PL-DBN) from BASF,Switzerland. In formulation 2 also 0.5 w % of 3-Trimethoxysilylpropylmethacrylate (Z-6030 from Dow Corning) was added.

To ensure a correct adhesion measure also during the curing process, athin layer of fast-curing acrylate based coating (UL1117, Becker-Acroma,Marsta, Sweden) was applied on top of our primer coatings to give aninvariant adhesion layer for the tape.

Before application of the primer, the wood sample panels were brushedclean from any loose particles, the plastic sample panels where washedwith soap and the metals were cleaned with toluene.

The thiol-ene-epoxy and thiol-methacrylate-epoxy formulations wereapplied on the substrates with a frame applicator with 10 μm gap andsubsequently cured under UV light (Mercury Lamp) until solid. Thereafterthe middle coat consisting of UL1117 was applied with an applicator with20 μm spacing and cured under UV light (Mercury lamp) until tested hardand non-sticky.

The cross-hatch adhesion tests were performed according to the ISOstandard 2409. Briefly, the test substrates were placed on a flat andrigid substrate and the cutting tool (6 blades, 1 mm apart) was used tocut two perpendicular cuts. The surface was brushed with a light brushand the tape (Scotch®, 600p) was applied on the cross-hatch and wasgently rubbed to ensure full contact. The tape was then pulled off atapproximately 60 deg angle during approximately 0.5 seconds. Theresulting surfaces were inspected under microscope and graded from 0 to5 according to the ISO 2409 standard. The results are presented in Table1.

TABLE 1 Sample material substrates and the adhesion according to ISO2409 2 h and 12 h respectively after application of the primer and amiddle coating. Primer Middle Sample Pre formulation coat Adhesion,Adhesion, material treatment (10 μm) (20 μm) 2 h 12 h Wood Oak none Form1 UL1117 0 0 Oak none Form 3 UL1117 1 0 Oak none Form 4 UL1117 4 2 Pinenone Form 1 UL1117 1 0 Stained pine none Form 1 UL1117 1 0 PlasticsPolyurethane none Form 1 UL1117 0 0 (PUR) Nitrilrubber none Form 1UL1117 0 0 (NBR) ABS none Form 4 UL1117 1 0 Metals Aluminum Toluene Form2 UL1117 1 0 Aluminum Toluene Form 3 UL1117 2 1 Aluminum Toluene Form 4UL1117 0 Cupper Toluene Form 2 UL1117 1 0 Stainless Toluene Form 2UL1117 0 0 steel Stainless Toluene Form 1 UL1117 1 0 steel Silicon wafer— Form 2 UL1117 0 0 (polished) Silicon wafer — Form 2 UL1117 0 0(polished) Glass — No 1 UL1117 1 0 (0 = excellent to 5 = no or very pooradhesion).

Example 2 Glass Transition Temperature and Mechanical Data

The glass transition temperature and storage modulus were analyzed usingDynamic Mechanical Analysis (DMA, Q800, PerkinElmer, Waltham, USA) fordifferent compositions of1,3,5-Triallyl-1,3,5-triazine-2,4,6(1H,3H,5H)-trione (TATATO),Pentaerythitol tetrakis(2-mercaptoacetate) (PETMP) and Epoxy NovolacD.E.N. 431. The initiator used where 1% Lucirin™ TPO-L and 1% of aphotolatent DBN (BASF, Switzerland).

The films were first polymerized using UV light but using a filterblocking all wavelengths under 400 nm. This initiated only the firstradical curing mechanism forming a solid polymer film. At a later point,these polymer films were irradiated by an unfiltered UV-light from aMercury lamp initiating the anionic curing mechanism. Table 2 shows datafrom DMA analysis taken after first cure (Formulation 5,6,7) and table 3after the second cure (Formulation 5,6,7,8,9). Note the narrow glasstransition that occurs during a very narrow temperature interval, herethe half height peak width of the tan 6 curve is displayed.

TABLE 2 DMA data for three different formulations after first cure. ΔTof glass transition at half Formu- Formu- Tg height peak width E-modulusE-modulus lation lation (° C.) of tan δ curve at 25° C. at 100° C. 5 r1= 1.25, r2 = 0.2 23 ± 0.4 20 ± 3 34 ± 5     3 ± 0.2 6 r1 = 1.5, r2 = 0.311 ± 2  13 ± 5 3.5 ± 0.6 1.5 ± 0 7 r1 = 1.5, r2 = 0.4 <0 Not meas.  1 ±0.2 0.5 ± 0

TABLE 3 DMA data for three different formulations after second cure. ΔTof glass transition at half Formu- Formu- Tg height peak width E-modulusE-modulus lation lation (° C.) of tan δ curve at 25° C. at 100° C. 5 r1= 1.25, r2 = 0.2 86 ± 0.4 17 ± 2 1780 ± 50  17.8 ± 0.3  6 r1 = 1.5, r2 =0.3 87 ± 0.9 19 ± 3 1830 ± 200 18 ± 0.5 7 r1 = 1.5, r2 = 0.4 87 ± 3.4 21± 2 2460 ± 450 17 ± 1  8 r1 = 1.25, r2 = 0.3 83 ± 3.2 21 ± 2 2300 ± 30016 ± 0.4 9 r1 = 1.25, r2 = 0.4 81 ± 4.1 25 ± 2 2400 ± 200 17 ± 0.6

Example 3 FT-IR Analysis of the Curing Mechanism

The polymerization was monitored using FT-IR transmission. Theformulation used was same as formulation 5 in example 2. A thin film ofthe prepolymer was squeezed between two NaCl crystals, irradiated withunfiltered UV to initiate both curing mechanisms at the same time. Thethiol peak (2575 cm⁻¹) and allyl peak (1644 cm⁻¹) were monitored duringpolymerization. Table 4 shows the area under each peak beforepolymerization (prepolymer), after 60 s and 180 s of UV irradiation andafter >24 h in 75° C. The allyl peak disappears during the first curingreaction and the thiol peak reduce in magnitude as part of the thiolsare reacted with the allyl monomers, but due to the off-stoichiometry alarge number of thiols are left unreacted. Over time these react withthe epoxy groups and disappeared after 12 h at room temperaturedemonstrating the rapid thiol-ene reaction and the slower thiol-epoxyreaction.

TABLE 4 Relative area (directly proportional to the respectiveconcentration of functional groups) under the thiol and allyl peaksduring curing compared to the prepolymer. Prepolymer 60 s UV 180 sUV >12 h at 25° C. Thiol peak 1 0.45 0.4 0 Allyl Peak 1 0.25 0 0

Example 4 Latent Curing

In another example formulations based on TATATO, PTMP and BADGE(Bisphenol A diglycidyl ether, Sigma-Aldrich Chemie GmbH) with 1% TPO-L(BASF, Germany) and 1% photo-latent DBN, PL-DBN (BASF, Switzerland). Themolar functional ratio was r1=1.4 and r2=0.3 (Formulation 10)

The dual curing process is carried out through two separated UV curingsteps. The TPO-L photo initiator triggers the thiol-ene reaction atwavelengths above 400 nm in the first step, the photolatent curing agentinitiates the thiol-epoxy reaction through the second curing step atwavelengths below 400 nm. In the first curing step light from a standardHg lamp is filtered to block light below 400 nm. In the second curingstep the Hg lamp is unfiltered.

The resulting material showed elastomeric and adhesive properties afterthe first curing step and was stiff and hard after the second curingprocess. The material that had undergone the first UV filtered UVexposure retained the same elastomeric mechanical property over time (upto a month) but hardened rapidly when exposed to unfiltered UV,demonstrating the fact that the curing processes could be successfullyseparated.

TABLE 5 Summary of experiment 4 Pre-polymer r1 = 1.4, r2 = 0.3, 1 w %TPO-L, 1 w % PL-DBN Curing order Curing step 1 Curing step 2 UV sourceMercury lamp with filter Unfiltered Mercury blocking wavelengths < 400lamp nm Stiffness E-modulus < 10 MPa, E-modulus > 1000 somewhat stickyMPa, dry Transparent Yes Yes Shelf-life Up to 1 week without Stable, allmonomers affecting mechanical reacted. Very little properties and stillcurable leachable components with a second curing step to in chloroform< 1%. a stiff polymer.

Example 5 Wafer Bonding

Wafer bonding (Ref: F. Forsberg et al, Proc. of MEMS 2013, pp. 343-346)was demonstrated using a formulation composed of TATATO, PTMP and DEN atr1=1.8 and r2=0.4 with 0.5 w % TPO-L and 0.1 w % DMP-30(2,4,6-(dimethylaminomethyl)phenol) from Polysciences Inc. (Formulation11)

The prepolymer was spun coated on a wafer at 6000 rpm. Formulation 11was in once case also diluted 1:1 in toluene before spinning andthereafter dried in vacuum at room temperature for 10 min. The filmswere subsequently exposed to unfiltered UV light from a Hg source (400mJ/cm² measured at 365 nm). This created a solid but a little stickylayer with unreacted thiol and epoxy groups. A SUSS Microtec SB8 waferbonder was used to bond the coated wafer and a lid silicon wafer. Thebonding processes started with pumping a vacuum (lower than 10⁻⁴ mbar)in the bond chamber, applying a bond force, pressing the waferstogether, and ramp the temperature to 90° C. The wafers were bonded witha 5000 N bond force together with a thermal curing time of 1 hour at 90°C.

Adhesion energy was evaluated by bonding two silicon wafers, with onehaving etched circular through holes. After bonding chips were diced outand the holes were connected to a nitrogen pressure source, which wereramped until the lid delaminated. The pressure at the start ofdelamination (burst pressure) was converted into bond energy γ using:

$p_{cr} = {\left( {\frac{32}{3\left( {1 - \upsilon^{2}} \right)}\left( \frac{h}{a} \right)^{3}} \right)^{\frac{1}{2}}\left( \frac{E\; \gamma_{a}}{a} \right)^{\frac{1}{2}}}$

Where h is the wafer thickness, a is the diameter of the circularorifice (here 12 mm), v is the Poisson ratio for Si (0.172, averagebetween <100> and <110>), E is the Young's modulus for Si (180 GPa) andγ_(a) is the adhesive fracture energy per square meter. All experimentsused Si lid wafers with a thickness of between 125 μm and 132 μm. Thebond energies for wafers bonded using BCB (Cyclotene 3022-46, DowChemical Company) and the nano imprint resist mr-I 9150 XP (Micro resisttechnology GmbH, Germany) were also measured using the same setup andbonding using the described bonding procedure in respective data sheets(thermal baking >200° C.). The results are presented in table 6.

TABLE 6 Adhesion energy between two Si wafers (4″) adhesively bondedusing different polymers. Lid Si Bond wafer layer Num- Mean thick-thick- ber of bond Standard Bonding Adhesion ness ness sam- energy,deviation layer promoter (μm) (μm) ples γ (J/m²) (J/m²⁾ BCB AP3000 1252.4 10 35 7.6 adhesion promoter (Dow chemical company) spun at 5000 rpmon the lid wafer BCB No 306 2.4 11 5.7 0.4 mr-I No 302 1.5 10 2.4 0.59150XP mr-I No 303 2.3 8 1.7 0.8 9150XP Formu- No 302 Not mea- 11 20 6.8lation 11 sured >3 μm Formu- No 132 3.9 11 2.2 2.0 lation 11 diluted 1:1in toluene before spinning

The results from table 6 demonstrates the disclosed formulations couldbe suitable as wafer bonding adhesive at processes requiring lowtemperatures. Moreover they are easily etched using oxygen plasmaenabling use as temporary wafer bond.

Example 6 UV-Vis and IR

The formulations were also tested for transparency in the UV-vis and IRregions after complete cure. In the UV-vis only the initiators areabsorbing under 400 nm. Between 400 nm to 900 nm, the absorption issimilar or close to that of COC (cylic olefin copolymers) or COP (cyclicolefin polymers).

UV-vis IR Formulation characteristics characteristics TATATO, PTMP, [300nm, 400 [900 nm, 2000 DEN r1 = 1.1 and nm]: high nm]: >95% r2 = 0.4 with1 w % absorption transparency TPO-L and 1 w % [400 nm, 900 Broad peakphoto-latent DBN nm]: >95% around 2500 nm (Formulation 12) transparency(hydroxyl groups) COC [300, 900 nm]: >95% transparency COP [300 nm, 900nm]: >97% transparency

Example 7 Barrier Properties

10 fresh pine substrates with knots were coated with Formulation 1 usinga 20 micrometer frame applicator and cured with two passes in a UV-ovenwith normal Hg-lamps (approx. 200 mJ/cm²). After about thirty minutes, awaterborne conventional outdoor coating with white pigmentation wasapplied at 150 g/m² via spray coating in order to get a white referencesurface. The panels were dried for 45 minutes in a constant heat oven(standard Sherwin-Williams protocols were used).

The samples were 1 week later subjected to 24 and 72 hrs of QUV light(accelerated weathering tester). Below is a summary of the comparisonbetween Formulation 1 and a commercial water borne primer (1422 ED 9003)from Sherwin-Williams with the same white pigmentation coating appliedon top. Experienced professionals assessed the yellowing on a scale from10 to 1 where 10 is the least yellowing (best).

24 h 24 h 24 h 24 h 72 h 72 h 72 h 72 h 72 h aver- Per- Per- Per- aver-Per- Per- Per- Per- age son 1 son 2 son 3 age son 1 son 2 son 3 son 4Formu- 8.0 7.9 8.8 7.8 8.9 9.2 9.6 8.3 8.4 lation 1 Com- 8.4 9 8.3 7.98.1 8.0 8.4 7.5 8.6 mercial primer

In terms of yellowing, i.e. barrier properties, Formulation 1 clearlyperforms at the same level as the currently used commercial primer.

1. A method for at least partially coating an object, said methodcomprising the steps: a) applying at least partially to said object atleast one of—: i. a compound comprising at least two thiol groups, ii. acompound comprising at least two carbon-carbon double bonds, and iii. acompound comprising at least two epoxide groups, and wherein ratio(r₁=t/cc) of the total number of thiol groups (t) in all of the abovecompounds and the total number of carbon-carbon double bonds (cc) in allof the above compounds is selected from the group consisting of0.1≦r₁≦0.9 and 1.1≦r₁≦20, with the proviso that if the ratio r₁ is inthe interval: 0.1≦r₁≦0.9, then at least one homopolymerizingene-compound is used, wherein ratio (r₂=t/e) of the total number ofthiol groups (t) in all of the above compounds and the total number ofepoxide groups (e) in all of the above compounds is in the range0.3≦r₂≦20, b) initiating a reaction of at least a part of the appliedcompound comprising at least two thiol groups with at least one of i. atleast a part of the applied compound comprising at least twocarbon-carbon double bonds and, ii. at least a part of the appliedcompound comprising at least two epoxide groups, iii. at least a part ofthe applied compound comprising at least one carbon-carbon double bondand at least one epoxide group, to obtain an intermediate at leastpartial coating, wherein said coating comprises at least one compoundcomprising an unreacted group selected from the group consisting of anunreacted thiol group, and an unreacted epoxide group, c) initiating areaction of at least a part of said at least one compound comprising anunreacted group, wherein at least one further coating is applied afterstep b) and before step c), to obtain to a final coated article.
 2. Themethod according to claim 1, wherein the reaction between at least apart of the applied compound comprising at least two thiol groups and atleast a part of the applied compound comprising at least one or twocarbon-carbon double bonds is initiated with at least one selected fromthe group consisting of actinic radiation, and elevated temperature. 3.The method according to claim 1, wherein the reaction of the at leastone compound comprising an unreacted group selected from the groupconsisting of an unreacted thiol group and an unreacted epoxide group isinitiated with at least one selected from the group consisting ofactinic radiation, and elevated temperature.
 4. The method according toclaim 1, wherein the reaction of the at least one compound comprising anunreacted group selected from the group consisting of an unreacted thiolgroup and an unreacted epoxide group is mediated with a basic compound.5. The method according to claim 1, wherein step b) and c) are initiatedsimultaneously.
 6. The method according to claim 1, wherein said atleast one further coating comprises at least one compound selected fromthe group consisting of a compound reactive with a thiol forming acovalent bond and a compound reactive with an epoxide to form a covalentbond.
 7. The method according to claim 1, wherein said at least onefurther coating comprises at least one compound comprising at least onechemical group selected from the group consisting of a hydroxyl group,an amine group, a thiol group, an anhydride group, a cyanoacrylategroup, an epoxide group, and a metal oxide.
 8. The method according toclaim 1, wherein said at least one further coating comprises at leastone compound comprising a chemical group selected from the groupconsisting of an acrylate, a methacrylate, a thiol, an isocyanate, amaleate, a fumarate, a vinyl ether, an alkene, an alkyne, an allylether.
 9. The method according to claim 1, wherein said at least onefurther coating comprises at least one selected from the groupconsisting of a metal, a polymer sheet, and a powder.
 10. The methodaccording to claim 1, wherein the surface of said object to be at leastpartially coated comprises at least one selected from the groupconsisting of a metal, a rubber, silicon, a thermoplastic elastomer,cellulose fibers, a textile, wood, a composite material, concrete, andstone.
 11. The method according to claim 1, wherein the object to be atleast partially coated is a printed circuit board.
 12. The methodaccording to claim 1, wherein said compound comprising at least twothiol groups is selected from the group consisting of pentaerythritoltetrakis (2-mercaptoacetate), pentaerythritol tetramercaptopropionate(PETMP); 1-octanethiol; butyl 3-mercaptopropionate;2,4,6-trioxo-1,3,5-triazina-triy (triethyl-tris (3-mercapto propionate);1,6-Hexanedithiol; 2,5-dimercaptomethyl-1,4-dithiane, pentaerythritoltetramercaptoacetate, trimethylolpropane trimercaptoacetate,2,3-dimercapto-1-propanol, 2,3-(dimercaptoethylthio)-1-mercaptopropane,1,2,3-trimercaptopropane, toluenedithiol, xylylenedithiol,1,8-octanedithiol, and trimethylolpropane tris(3-mercaptopropionate),and glycol dimercaptopropionate and pentaerythritoltetramercaptopropionate (PETMP).
 13. The method according to claim 1,wherein said compound comprising at least two carbon-carbon double bondsis selected from the group consisting oftriallyl-1,3,5-triazine-2,4,6(1H,3H,5H)-trione; triethyleneglycoldivinyl ether (TEGDVE); trimethylolpropane diallyl ether;1,6-heptadiyne; 1,7-octadiyne;bis-2,2-[4-(2-[norborn-2-ene-5-carboxylate]ethoxy)phenyl]propane(BPAEDN); 1,6-hexanediol di-(endo,exo-norborn-2-ene-5-carboxylate)(HDDN); trimethylolpropane tri-(norborn-2-ene-5-carboxylate) (TMPTN);pentaerythritoltri-(norborn-2-ene-5-carboxylate) (PTN3); pentaerythritoltetra-(norborn-2-ene-5-carboxylate) (PTN4); tricyclodecane dimethanoldi-(endo, exo-norborn-2-ene-5-carboxylate) (TCDMDN); anddi(trimethylolpropane) tetra-(norbom-2-ene-5-carboxylate) (DTMPTN). 14.The method according to claim 1, wherein said compound comprising atleast two epoxide groups is selected from the group consisting ofTris(2,3-epoxidepropyl) isocyanurate, trimethylolpropane triglycidylether, tris(4-hydroxyphenyl)methane triglycidyl ether, poly(ethyleneglycol) diglycidyl ether, bisphenol A diglycidyl ether1,2,5,6-diepoxidecyclooctane, 1,2,7,8-diepoxideoctane,1,2-Epoxide-5-hexene, 1,4-cyclohexanedimethanol diglycidyl ether,3,4-epoxidecyclohexylmethyl 3,4-epoxidecyclohexanecarboxylate,4,4′-methylenebis(N,N-diglycidylaniline),bis[4-(glycidyloxy)phenyl]methane, bis[4-(glycidyloxy)phenyl]methane,diglycidyl 1,2-cyclohexanedicarboxylate,N,N-diglycidyl-4-glycidyloxyaniline, neopentyl glycol diglycidyl ether,resorcinol diglycidyl ether, and tris(4-hydroxyphenyl)methanetriglycidyl ether.
 15. The method according to claim 1, wherein saidcompound comprising at least two epoxide groups is allylglycidylether.16. The method according to claim 1, wherein the thickness of thecompounds added in step a) is in the interval 2-100 μm.
 17. The methodaccording to claim 1, wherein said at least one homopolymerizingene-compound is selected from the group consisting of acrylate andmethacrylate.
 18. A coated object comprising a coating which is at leastpartially applied to said object, said coating comprising: a) covalentbonds formed by reaction of a thiol group and a carbon-carbon doublebond, b) covalent bonds formed by reaction of a thiol group and epoxidegroup, c) covalent bonds formed by a reaction of a carbon-carbon doublebond and an epoxide group, said coating comprising a first coating and asecond coating, said coating comprising covalent bonds between saidfirst and second coatings, said first coating comprising covalent crosslinks between compounds, in the first coating the fraction (r₃=ta/tc) ofunreacted thiol groups (ta) to thiol groups which have reacted to form acovalent bond (tc) does not exceed 0.11, wherein, for the first coatingthe half height peak width of tan delta does not exceed 30° C., said tandelta peak temperature (Tp) and said half height peak width beingobtained from a viscoelasticity (tan delta) temperature distributioncurve which is determined using a viscoelastic spectrometer at afrequency of 1 Hz, an initial strain of 1%, an amplitude of 15 μm and atemperature elevating rate of 5° C./min, temperatures being equal to andgreater than Tp to the temperature defined by the point of intersectionof the line of tan delta=1/2P, wherein P is the peak value of tan δ,with the distribution curve.
 19. The coated object according to claim18, wherein said second coating comprises at least one compoundcomprising at least one chemical group selected from the groupconsisting of a hydroxyl group, an amine group, a thiol group, ananhydride group, a cyanoacrylate group, an epoxide group, and a metaloxide.
 20. The coated object according to claim 18, wherein said secondcoating comprises at least one compound comprising a chemical groupselected from the group consisting of an acrylate, a methacrylate, athiol, an isocyanate, a maleate, a fumarate, a vinyl ether, an alkene,an alkyne, an allyl ether.
 21. The coated object according to claim 18,wherein said second coating comprises at least one selected from thegroup consisting of a metal, a polymer sheet, and a powder.
 22. Thecoated object according to claim 18, wherein the surface of said objectcomprises at least one selected from the group consisting of a metal, arubber, silicon, a thermoplastic elastomer, cellulose fibers, a textile,wood, a composite material, concrete, and stone.
 23. The coated objectaccording to claim 18, wherein the object to be at least partiallycoated is a printed circuit board.
 24. The coated object according toclaim 18, wherein the first coating comprises at least one compoundselected from the group consisting of pentaerythritol tetrakis(2-mercaptoacetate), pentaerythritol tetramercaptopropionate (PETMP);1-octanethiol; butyl 3-mercaptopropionate;2,4,6-trioxo-1,3,5-triazina-triy (triethyl-tris (3-mercapto propionate);1,6-Hexanedithiol; 2,5-dimercaptomethyl-1,4-dithiane, pentaerythritoltetramercaptoacetate, trimethylolpropane trimercaptoacetate,2,3-dimercapto-1-propanol, 2,3-(dimercaptoethylthio)-1-mercaptopropane,1,2,3-trimercaptopropane, toluenedithiol, xylylenedithiol,1,8-octanedithiol, and trimethylolpropane tris(3-mercaptopropionate),and glycol dimercaptopropionate and pentaerythritoltetramercaptopropionate (PETMP), wherein at least one thiol group hasformed a covalent bond with at least one selected from a carbon-carbondouble bond and an epoxide group.
 25. The coated object according toclaim 18, wherein the first coating comprises at least one compoundselected from the group consisting oftriallyl-1,3,5-triazine-2,4,6(1H,3H,5H)-trione; triethyleneglycoldivinyl ether (TEGDVE); trimethylolpropane diallyl ether;1,6-heptadiyne; 1,7-octadiyne;bis-2,2-[4-(2-[norborn-2-ene-5-carboxylate]ethoxy)phenyl]propane(BPAEDN); 1,6-hexanediol di-(endo,exo-norborn-2-ene-5-carboxylate)(HDDN); trimethylolpropane tri-(norborn-2-ene-5-carboxylate) (TMPTN);pentaerythritoltri-(norborn-2-ene-5-carboxylate) (PTN3); pentaerythritoltetra-(norborn-2-ene-5-carboxylate) (PTN4); tricyclodecane dimethanoldi-(endo, exo-norborn-2-ene-5-carboxylate) (TCDMDN); anddi(trimethylolpropane) tetra-(norbom-2-ene-5-carboxylate) (DTMPTN),wherein at least one carbon-carbon double bond has formed a covalentbond with at least one selected from a thiol group and an epoxide group.26. The coated object according to claim 18, wherein the first coatingcomprises at least one compound selected from the group consisting ofTris(2,3-epoxidepropyl) isocyanurate, trimethylolpropane triglycidylether, tris(4-hydroxyphenyl)methane triglycidyl ether, poly(ethyleneglycol) diglycidyl ether, bisphenol A diglycidyl ether1,2,5,6-diepoxidecyclooctane, 1,2,7,8-diepoxideoctane,1,2-Epoxide-5-hexene, 1,4-cyclohexanedimethanol diglycidyl ether,3,4-epoxidecyclohexylmethyl 3,4-epoxidecyclohexanecarboxylate,4,4′-methylenebis(N,N-diglycidylaniline),bis[4-(glycidyloxy)phenyl]methane, bis[4-(glycidyloxy)phenyl]methane,diglycidyl 1,2-cyclohexanedicarboxylate,N,N-diglycidyl-4-glycidyloxyaniline, neopentyl glycol diglycidyl ether,resorcinol diglycidyl ether, and tris(4-hydroxyphenyl)methanetriglycidyl ether, wherein at least one epoxide group has formed acovalent bond with at least one selected from a thiol group and acarbon-carbon double bond.
 27. The coated object according to claim 18,wherein the thickness of the coating is in the interval 0.01-2000 μm.28. The coated object according to claim 18, wherein the coating forms abarrier impermeable to liquid.